Delivery system for placement of prosthesis at luminal os

ABSTRACT

An embodiment of the invention provides a prosthesis delivery system comprising a delivery catheter having an expandable member and a prosthesis carried over the expandable member. The prosthesis includes a radially expandable scaffold section and at least two anchors extending axially from an end thereof, and means for capturing at least the anchors to prevent the anchors from divaricating from the expandable member as the catheter is advanced through a patient&#39;s vasculature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to medical devicesand methods. More particularly, embodiments of the present inventionrelate to the structure and deployment of a segmented stent at a luminalos at a branching point in the vasculature or elsewhere.

Maintaining the patency of body lumens is of interest in the treatmentof a variety of diseases. Of particular interest to the presentinvention are the transluminal approaches to the treatment of bodylumens. More particularly, the percutaneous treatment of atheroscleroticdisease involving the coronary and peripheral arterial systems.Currently, percutaneous coronary interventions (PCI) often involve acombination of balloon dilation of a coronary stenosis (i.e. a narrowingor blockage of the artery) followed by the placement of an endovascularprosthesis commonly referred to as a stent.

A major limitation of PCI/stent procedures is restenosis, i.e., there-narrowing of a blockage after successful intervention typicallyoccurring in the initial three to six months post treatment. The recentintroduction of drug eluting stents (DES) has dramatically reduced theincidence of restenosis in coronary vascular applications and offerspromise in peripheral stents, venous grafts, arterial and prostheticgrafts, as well as A-V fistulae. In addition to vascular applications,stents are being employed in treatment of other body lumens includingthe gastrointestinal systems (esophagus, large and small intestines,biliary system and pancreatic ducts) and the genital-urinary system(ureter, urethra, fallopian tubes, vas deferens).

Treatment of lesions in and around branch points generally referred toas bifurcated vessels, is a developing area for stent applications,particularly, since 10% of all coronary lesions involve bifurcations.However, while quite successful in treating arterial blockages and otherconditions, most stent designs are challenged when used at a bifurcationin the blood vessel or other body lumen. Presently, many differentstrategies are employed to treat bifurcation lesions with currentlyavailable stents all of which have major limitations.

One common approach is to place a conventional stent in the main orlarger body lumen over the origin of the side branch. After removal ofthe stent delivery balloon, a second wire is introduced through a cellin the wall of the deployed stent and into the side branch. A balloon isthen introduced into the side branch and inflated to enlarge theside-cell of the main vessel stent. This approach can work well when theside branch is relatively free of disease, although it is associatedwith increased rates of abrupt closure due to plaque shift as well asincreased rates of late re-restenosis.

Another commonly employed strategy is the ‘kissing balloon’ technique inwhich separate balloons are positioned in the main and side branchvessels and simultaneously inflated to deliver separate stentssimultaneously. This technique is thought to prevent plaque shift.

Other two stent approaches including Culotte, T-Stent and Crush Stenttechniques have been employed as well. When employing a T-stentapproach, the operator deploys a stent in the side branch followed byplacement of a main vessel stent. This approach is limited by anatomicvariation (angle between main and side branch) and inaccuracy in stentpositioning, which together can cause inadequate stent coverage of thesidebranch os. More recently, the Crush approach has been introduced inwhich the side-vessel stent is deployed across the os with portions inboth the main and side branch vessels. The main vessel stent is thendelivered across the origin of the side branch and deployed, whichresults in crushing a portion of the side branch stent against the wallof the main vessel. Following main-vessel stent deployment, it isdifficult and frequently not possible to re-enter the side branch aftercrush stenting. Unproven long-term results coupled with concernregarding the inability to re-enter the side branch, malaposition of thestents against the arterial wall and the impact of three layers of stent(which may be drug eluting) opposed against the main vessel wall haslimited the adoption of this approach.

These limitations have led to the development of stents specificallydesigned to treat bifurcated lesions. One approach employs a stentdesign with a side opening for the branch vessel which is mounted on aspecialized delivery balloon. The specialized balloon delivery systemaccommodates wires for both the main and side branch vessels. The systemis tracked over both wires which provides a mean to axially and radiallyalign the stent/stent delivery system. The specialized main vessel stentis then deployed and the stent delivery system removed while maintainingwire position in both the main and side branch vessels. The side branchis then addressed using kissing balloon or by delivering and anadditional stent to the side branch. Though this approach has manytheoretic advantages, it is limited by difficulties in tracking thedelivery system over two wires (Vardi et al, U.S. Pat. Nos. 6,325,826and 6,210,429).

Another approach, of particular interest to the present invention,includes the use of fronds, or fingers extending from the scaffolding ofa side branch stent to facilitate positioning of the stent at abifurcated lesion. This approach is described in detail in co-pendingcommonly assigned application Ser. No. 10/807,643 the full disclosure ofwhich is incorporated herein.

However while above approach has significant promise, conventional stentdelivery systems, such as balloon catheters, can have difficultymanaging the fronds during delivery. In such conventional systems, thestent is usually crimped onto the balloon of the balloon catheter. Whilefine for many conventional stent designs, conventional balloons systemsmay not always prevent the fronds on a stent from separating from theballoon as the catheter is advanced through curved portions of thevasculature, such as those found in the circumflex coronary artery.

For these reasons, it would be desirable to provide improved systems andmethods for delivering stents, particularly stents with fronds or otherprotruding anchoring elements at one end, to treat body lumens at ornear the location of an os between a main body lumen and a side branchlumen, typically in the vasculature, and more particularly in thearterial vasculature. It would be further desirable if such systems andmethods could treat the side branch vessels substantially completely inthe region of the os and that the prostheses in the side branches bewell-anchored at or near the os.

2. Description of the Background Art

Stent structures intended for treating bifurcated lesions are describedin U.S. Pat. Nos. 6,599,316; 6,596,020; 6,325,826; and 6,210,429. Otherstents and prostheses of interest are described in the following U.S.Pat. Nos. 4,994,071; 5,102,417; 5,342,387; 5,507,769; 5,575,817;5,607,444; 5,609,627; 5,613,980; 5,669,924; 5,669,932; 5,720,735;5,741,325; 5,749,825; 5,755,734; 5,755,735; 5,824,052; 5,827,320;5,855,598; 5,860,998; 5,868,777; 5,893,887; 5,897,588; 5,906,640;5,906,641; 5,967,971; 6,017,363; 6,033,434; 6,033,435; 6,048,361;6,051,020; 6,056,775; 6,090,133; 6,096,073; 6,099,497; 6,099,560;6,129,738; 6,165,195; 6,221,080; 6,221,098; 6,254,593; 6,258,116;6,264,682; 6,346,089; 6,361,544; 6,383,213; 6,387,120; 6,409,750;6,428,567; 6,436,104; 6,436,134; 6,440,165; 6,482,211; 6,508,836;6,579,312; and 6,582,394.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention provide improved delivery systemsfor the delivery and placement of stents or other prosthesis within abody lumen, particularly within a bifurcated body lumen and moreparticularly at an os opening from a main body lumen to a branch bodylumen. The delivery systems will be principally useful in thevasculature, most typically the arterial vasculature, including thecoronary, carotid and peripheral vasculature; vascular grafts includingarterial, venous, and prosthetic grafts, and A-V fistulae. In additionto vascular applications, embodiments of the present invention can alsobe configured to be used in the treatment of other body lumens includingthose in the gastrointestinal systems (e.g., esophagus, large and smallintestines, biliary system and pancreatic ducts) and the genital-urinarysystem (e.g., ureter, urethra, fallopian tubes, vas deferens), and thelike.

The stent or other prostheses to be delivered will usually comprise aproximal portion which can include anchoring components which caninclude anchors, fronds, petals or other independently deflectableelement extending axially from a main or scaffold section of the stent.These anchoring components can expandably conform to and at leastpartially circumscribe the wall of the main body vessel to selectivelyand stably position the prosthesis within the side branch lumen. Furtherdescription of exemplary anchoring components and prostheses is found inco-pending application Ser. No. 10/897,643, the full disclosure of whichhas previously been incorporated herein by reference. Variousembodiments of the present invention provide means for capturing orotherwise radially constraining the anchoring components duringadvancement of the stent through the vasculature (or other body lumen)to a target site and then releasing the anchoring components.

In a first aspect of the invention, a prosthesis delivery systemcomprises a delivery catheter having an expandable member and aprosthesis carried over the expandable member. The prosthesis has aradially expandable scaffold and at least two fronds extending axiallyfrom an end of the scaffold. The system also includes means forcapturing the fronds to prevent them from divaricating from theexpandable member as the catheter is advanced through a patient'svasculature. Divarication as used herein means the separation orbranching of the fronds away from the delivery catheter. Variousembodiment of the capture means prevent divarication by constrainingand/or imparting sufficient hoop strength to the fronds to prevent themfrom branching from the expandable member during catheter advancement inthe vasculature.

In one embodiment, the capturing means comprises a portion of theexpandable member that is folded over the fronds where the foldsprotrude through axial gaps between adjacent fronds. In anotherembodiment, the capturing means comprises a cuff that extends over atleast a portion of the fronds to hold them during catheter advancement.The cuff can be positioned at the proximal end of the prosthesis and canbe removed by expansion of the expandable member to either plasticallydeform the cuff, break the cuff, or reduce the cuff in length axially asthe cuff expands circumferentially. The cuff is then withdrawn from thetarget vessel. In yet another embodiment, the capturing means cancomprise a tether which ties together the fronds. The tether can beconfigured to be detached from the fronds prior to expansion of theexpandable member. In alternative embodiments, the tether can beconfigured to break or release upon expansion of the expandable memberso as to release the fronds.

In an exemplary deployment protocol using the prosthesis deliverysystem, the delivery catheter is advanced to position the prosthesis ata target location in a body lumen. During advancement, at least aportion of the fronds are radially constrained to prevent divaricationof the fronds from the delivery catheter. When the target location isreached, the radial constraint is released and the prosthesis isdeployed within the lumen.

In various embodiments, the release of the fronds and expansion of theprosthesis can occur simultaneously or alternatively, the radialconstraint can be released prior to expanding/deploying the prosthesis.In embodiments where the radial constraint comprises balloon foldscovering the fronds or a cuff or tether, the constraint can be releasedas the balloon is inflated. In alternative embodiments using a cuff ortether, the cuff/tether can be withdrawn from the fronds prior toexpansion of the scaffold.

Embodiments of the above protocol can be used to deploy the prosthesisacross the os of a branch body lumen into the main body lumen. In suchapplications, the prosthesis can be positioned so that the scaffold lieswithin the branch body and at least two fronds extend into the main bodylumen. The fronds are then circumferentially deformed to circumscribe atleast a portion of the main vessel wall and open a passage through thefronds. At least three fronds extend into the main body lumen.

Radiopaque or other medical imaging visible markers can be placed on theprostheses and/or delivery balloon at desired locations. In particular,it may be desirable to provide radiopaque markers at or near thelocation on the prosthesis where the scaffold is joined to thecircumferential fronds. Such markers will allow a transition region ofthe prosthesis between the scaffold and the fronds to be properlylocated near the os prior to scaffold expansion. The radiopaque or othermarkers for location the transition region on the prosthesis can also bepositioned on a balloon or other delivery catheter. Accordingly, in oneembodiment of the deployment protocol, positioning the prosthesis caninclude aligning a visible marker on at least one of the prosthesis anda delivery balloon with the os.

In various embodiments for deploying the prosthesis, the scaffold isexpanded with a balloon catheter expanded within the scaffold. In someinstances, the scaffold and the circumferential fronds may be expandedand deformed using the same balloon, e.g., the balloon is first used toexpand the anchor, partially withdrawn, and then advanced transverselythrough the circumferential fronds where it is expanded for a secondtime. Alternatively, separate balloon catheters may be employed forexpanding the scaffold within the side branch and deforming thecircumferential fronds within the main body lumen.

By “expandably circumscribe,” it is meant that the fronds will extendinto the main body lumen after initial placement of the scaffold withinthe branch body lumen. The circumferential fronds will be adapted tothen be partially or fully radially expanded, typically by expansion ofa balloon or other expandable element therein, so that the fronds deformoutwardly and engage the interior of the main lumen wall.

The circumferential fronds will usually extend axially within the mainvessel lumen for some distance after complete deployment. Thus, thecontact between the fronds and the main vessel wall will usually extendboth circumferentially (typically covering an arc equal to one-half ormore of the circumference) and axially.

Expansion of the circumferential fronds at least partially within themain body lumen provides a generally continuous coverage of the os fromthe side body lumen to the main body lumen. Further and/or completeexpansion of the circumferential fronds within the main body lumen maypress the fronds firmly against the main body lumen wall and open up thefronds so that they do not obstruct flow through the main body lumen.

Usually, the prosthesis will include at least three circumferentialfronds extending axially from the end of the scaffold. Thecircumferential fronds will have an initial length (i.e., prior toradial expansion of the scaffold) which is at least 1.5 times the widthof the scaffold prior to expansion, typically being at least 2 times thewidth, more typically being at least 5 times the width, and often being7 times the width or greater. The lengths will typically be at least 2mm, preferably being at least 3 mm, and more preferably being at least 6mm, depending on the diameter of the scaffold and prosthesis. Thecircumferential fronds will usually have a width which is expandable toaccommodate the expansion of the scaffold, and the fronds may be“hinged” at their point of connection to the scaffold to permit freedomto adapt to the geometry of the main vessel lumen as the prosthesis isexpanded. It is also possible that the fronds could be attached to thesingle point to the scaffold, thus reducing the need for suchexpandability. The fronds may be congruent, i.e., have identicalgeometries and dimensions, or may have different geometries and/ordimensions. In particular, in some instances, it may be desirable toprovide fronds having different lengths and/or different widths. Againfurther description of the fronds may be found in co-pending applicationSer. No. 10/807,643.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prosthesis constructed inaccordance with the principles of the present invention.

FIG. 1A is a detailed view of an fronds of the prosthesis of FIG. 1,shown with the fronds deployed in broken line.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1.

FIGS. 3A and 3B are lateral and cross sectional views illustrating anembodiment of a stent having fronds and an underlying deployment balloonhaving a fold configuration such that the balloon folds protrude throughthe spaces between the fronds.

FIGS. 4A and 4B are lateral and cross sectional views illustrating theembodiment of FIGS. 3A and 3B with the balloon folded over to capturethe fronds.

FIGS. 5A-5C are lateral views illustrating the deployment of stentfronds using an underlying deployment balloon and a retaining cuffpositioned over the proximal portion of the balloon. FIG. 5A showspre-deployment, the balloon un-inflated; FIG. 5B shows deployment, withthe balloon inflated; and FIG. 5C post-deployment, the balloon nowdeflated.

FIGS. 6A-6B are lateral views illustrating the change in shape of thecuff of during deployment of a stent with fronds, of FIG. 6A shows theballoon in an unexpanded state; and FIG. 6B shows the balloon in anexpanded state, with the cuff expanded radially and shrunken axially.

FIGS. 6C-6D are lateral views illustrating an embodiment of a cuffconfigured to evert upon balloon inflation to release the fronds.

FIGS. 7A-7B are lateral views illustrating an embodiment of a tether forrestraining the stent fronds.

FIGS. 8A-8B are lateral views illustrating an embodiment of a movablesleeve for restraining the stent fronds.

FIGS. 9A-9B, 10A-10B and 11A-11B illustrate deployment of a stent at anos between a main blood vessel and a side branch blood vessel inaccordance with the principles of the methods of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1 and 2, an embodiment of a delivery system 5 ofthe present invention for the delivery of a stent to a bifurcated vesselcan include a stent or other prosthesis 10 and a delivery catheter 30.Stent 10 can include at least a radially expansible scaffold section 12and an anchor section 14 with one or more anchors 16 also known asfronds 16. In various embodiments, the anchor section 14 includes atleast two axially aligned circumferential fronds 16, with three beingillustrated. The radially expansible scaffold section 12 will typicallybe expandable by an expansion device such as a balloon catheter, butalternatively it can be self expandable. The scaffold section may beformed using a variety of conventional patterns and fabricationtechniques as are well-described in the prior art.

Fronds 16, will usually extend axially from the scaffold section 12, asillustrated, but in some circumstances the fronds can be configured toextend helically, spirally, in a serpentine pattern, or otherconfigurations. It is desirable, however, that the individual fronds beradially separable so that they can be independently folded, bent, andotherwise positioned within the main body lumen after the scaffoldsection 12 has been implanted within the branch body lumen. In theschematic embodiment of FIG. 1, the fronds 16 may be independentlyfolded out in a “petal-like” configuration, forming petals 16 p, asgenerally shown in broken line for one of the fronds in FIGS. 1 and 2.

In preferred embodiments, fronds 16 will be attached to the scaffoldsection 12 such that they can both bend and rotate relative to an axis Athereof, as shown in broken line in FIG. 1A. Bending can occur radiallyoutwardly and rotation or twisting can occur about the axis A as thefronds are bent outwardly. Such freedom of motion can be provided bysingle point attachment joints as well as two point attachments orthree-point attachments.

Referring now to FIGS. 3A-8, in various embodiments delivery system 5can include a stent 210 having fronds 220 which are configured to becaptured or otherwise radially constrained during advancement of thestent through the vasculature or other body lumen. As shown in FIGS.3A-3B, fronds 220 can be separated by axial gaps or splits 230 along thelength of the stent structure. Splits 230 can have a variety of widthsand in various embodiments, can have a width between 0.05 to 2 times thewidth of the fronds, with specific embodiments of 0.05, 0.25, 0.5, 1 and2 times the width of the fronds. Fronds 220 can be configured to havesufficient flexibility to be advanced through curved and/or tortuousvessels to reach the more distal portions of the vasculature such asdistal portion of the coronary vasculature. This can be achieved throughthe selection of dimensions and/or material properties (e.g. flexuralproperties) of the fronds. For example, all or a portion of fronds 220can comprise a resilient metal (e.g., stainless steel) or a superelasticmaterial known in the art. Examples of suitable superelastic materialsinclude various nickel titanium alloys known in the art such asNitinol™.

It is desirable to have the fronds captured and held against thedelivery catheter or otherwise restrained as the stent is advancedthrough the vasculature in order to prevent the fronds from divaricatingor separating and branching from the scaffold section of the stent.Capture of the fronds and prevention of divarication can be achievedthrough a variety of means. For example, in various embodiments thecapture means can be configured to prevent divarication by impartingsufficient hoop strength to the fronds, or a structure including thefronds, to prevent the fronds from separating and branching from thedeployment balloon as the balloon catheter is advanced through thevascular including tortuous vasculature. In theses embodiments, thecapture means are also configured to allow the fronds to have sufficientflexibility to be advanced through the vasculature as described above.

In an embodiment shown in FIGS. 3A-4B, the fronds can be captured underthe flaps 242 of a deployment balloon 241 of a delivery balloon catheter240. In this and related embodiments, the balloon 241 and stent 210 canbe configured such that flaps 242 are substantially matched up oraligned with splits 230. This can achieved using alignment techniquesknown in the art (e.g., use of alignment fixtures) when the stent 220 ispositioned over balloon 241. The flap material will initially extend orprotruded through the splits, but is then folded over onto one or morefronds 220 to capture those fronds. In an embodiment, this can beachieved by partially inflating and then deflating the balloon, withfolding done after the inflation or deflation. Folding can be done byhand or using a capture tube or overlying sleeve known in the art. Alsoin an embodiment, folding can be facilitated by the use of one or morepreformed folds 243, also known as fold lines 243. Folds 243 can beformed using medical balloon fabrication methods known in the art suchas mold blowing methods known in the art. In an embodiment using folds243, folding can be achieved by inflating the balloon with the overlyingfronds in place, so as to have the balloon flaps 242 protrude throughsplits 230, then the balloon is a deflated to have flaps 242 fold backover fronds 220 at fold lines 243.

Once stent 210 is properly positioned at the target vessel site, balloon241 is at least partially inflated which unfurls flaps 242 coveringfronds 220 so as to release the fronds. Once released, deploymentballoon 241 can also be used to expand or otherwise deform the fronds220 to deploy them in the selected vessel as is described herein.Alternatively, a second balloon can be to used expand and deploy thefronds as is also described herein.

To avoid pinching the balloon material of balloon 241 between layers ofstent metal during the stent crimping process in one embodiment, fronds220 can be configured such that they do not overlap when crimped down toa smaller diameter. This can be achieved by configuring the fronds to besufficiently narrow so that crimping the stent to a smaller diameterdoes not cause them to overlap, or through the use of a crimping fixtureor mandrel known in the art. In various embodiments, fronds 220 can beconfigured to have a selectable minimum split width 230 w between splits230 after crimping. This can be in the range of about 0.001 to about 0.2inches with specific embodiments of 0.002, 0.005, 0.010, 0.025, 0.050and 0.1 inches.

In another embodiment for using the delivery balloon catheter to capturethe fronds, a section of the balloon 241 (not shown) can be configuredto evert or fold back over a proximal portion of the stent and thusoverly and capture the fronds. When the balloon is inflated, theoverlying section of balloon material unfolds, releasing the fronds. Theeverted section of balloon can over all or any selected portion of thefronds. Eversion can be facilitated through the use of preformed foldsdescribed herein, in this case, the folds having a circumferentialconfiguration. The folded section of balloon can be held in place by afriction fit or through the use of releasable low-strength heat bond oradhesive known in the art for bonding the balloon to the fronds. In oneembodiment for positioning the everted section, the balloon ispositioned inside the scaffold section of the stent and then partiallyinflated to have an end of the balloon protrude outside of the scaffoldsection, then the balloon is partially deflated and the everted sectionis rolled over the fronds and then the balloon is fully deflated tocreate a vacuum or shrink fit of the balloon onto the fronds.

In various embodiments, fronds 210 can also be captured by use of a cuff250 extending from the proximal end 241 p of delivery balloon 241 as isshown in FIGS. 5A-5C. In preferred embodiments the cuff is attached tothe catheter at the proximal end 241 p of the delivery balloon. Inalternative embodiments, the cuff can be attached to a more proximalsection of the catheter shaft such that there is an exposed section ofcatheter shaft between balloon and the cuff attachment point with theattachment point selected to facilitate catheter flexibility. In eitherapproach, the cuff is fixed to the proximal end of the balloon 241 psuch that it overlies at least a portion of stent fronds 220.

After stent 210 is positioned at the target tissue site, the cuffreleases the fronds allowing the stent to be deployed using the deliveryballoon as is described herein. After releasing the fronds, the cuff canthen be withdrawn prior to or along with the removal of the ballooncatheter. In most embodiments, the entire catheter assembly includingcuff, balloon, and catheter shaft are withdrawn proximally to fullyrelease the fronds.

Release of the fronds by the cuff can be achieved through a variety ofmeans. In one embodiment, cuff 250 can be configured such the frond tips220 t, slip out from the cuff when the balloon is deployed.Alternatively, the cuff my scored or perforated such that it breaks atleast partially open upon balloon deployment so that it releases fronds220. Accordingly, in such embodiments, cuff 250 can have one or morescored or perforated sections 250 p. In such embodiments, portions ofcuff 250 can be configured to break open at a selectable inflationpressure or at a selectable expanded diameter.

In various embodiments, cuff 250 can be configured such that itplastically deforms when the balloon is inflated and substantiallyretains its “inflated shape” 250 is and “inflated diameter” 250 id afterthe balloon is deflated is shown in FIGS. 5B and 5C. This can beachieved through the selection of plastically deformable materials forcuff 250 (e.g. plastically deformable polymers), the design of the cuffitself (e.g. cuff dimensions and shape) and combinations thereof. Forexample, a cuff fixed to the catheter shaft and having the sameapproximate internal diameter as the deployed stent may be folded overthe stent fronds to constrain them (using conventional balloon foldingtechniques). That cuff may be unfolded when the stent deployment balloonis inflated and the fronds released. The cuff can then be withdrawnalong with the balloon and catheter. In an alternative embodiment of afolded-over cuff, the cuff is relatively inelastic and has an internaldiameter approximately that of the deployed stent.

Also the cuff can be configured such that it shortens axially as it isexpanded by the deployment balloon or other expansion device. This canbe accomplished by selecting the materials for cuff 250 such that cuffshrinks axially when it is stretched radially as is shown in FIGS. 6Aand 6B. Accordingly, in one embodiment, the cuff can made of elastomericmaterial configured to shrink axially when stretched radially.

In another embodiment, all or a portion of the cuff can be configured tofold over or evert onto itself upon inflation of the balloon to producean everted section 251 and so release the enveloped fronds as is shownin FIGS. 6C-6D. This can be facilitated by use of fold lines 252described herein, as well as coupling the cuff to the balloon catheter.In one embodiment the cuff can be coaxially disposed over the proximalor distal end of the balloon catheter or even slightly in front ofeither end. This allows the cuff to disengage the fronds yet remainattached to the balloon catheter for easy removal from the vessel. Inuse, these and related embodiments allow the fronds to be held againstthe balloon to be radially constrained or captured during stentadvancement and then easily released before, during or after ballooninflation to deploy the stent at the target site.

In various embodiments, all or a portion of cuff 250 can be fabricatedfrom, silicones, polyurethanes (e.g., PEPAX) and other medicalelastomers known in the art; polyethylenes; fluoropolymers; polyolefin;as well as other medical polymers known in the art. Cuff 250 can also bemade of heat shrink tubing known in the art such as polyolefin or PTFEheat shrink tubing. These materials can be selected to produce a desiredamount of plastic deformation for a selected stress (e.g. hoop stressfrom the inflation of deployment balloon). In particular embodiments,all or a portion of the materials comprising cuff 250 can be selected tohave an elastic limit lower than forces exerted by inflation of thedeployment balloon (e.g., the force exerted by a 3 mm diameter ballooninflated to 10 atms). Combinations of materials may be employed suchthat different portions of the cuff (e.g., the proximal and distalsections or the inner and outer surfaces) have differing mechanicalproperties including, but not limited to, durometer, stiffness andcoefficient of friction. For example, in one embodiment the distalportion of the cuff can high a higher durometer or stiffness than aproximal portion of the cuff. This can be achieved by constructing theproximal portion of the cuff from a first material (e.g., a firstelastomer) and the distal portion out of a second material (e.g. asecond elastomer). Embodiments of the cuff having a stiffer distalportion facilitate maintaining the fronds in a restrained state prior todeployment. In another embodiment, at least a portion of an interiorsurface of the cuff can include a lubricous material. Examples ofsuitable lubricious materials include fluoropolymers such as PTFE. In arelated embodiment, a portion of the interior of the cuff, e.g., adistal portion, can be lined with a lubricous material such as afluoropolymer. Use of lubricous materials on the interior of the cuffaids in the fronds sliding out from under the cuff during balloonexpansion.

Referring now to FIGS. 7A-7B, in another embodiment for restraining thefronds, a tether 260 can be placed over all or portion of fronds 220 soas to tie the fronds together. Similar to the use of cuff 250, tether260 can be released by the expansion of the balloon 241. Accordingly,all or a portion of the tether can be configured to plastically deformupon inflation of balloon 241 so as to release the fronds.Alternatively, the tether can be configured to be detached from thefronds prior to expansion of the balloon. In one embodiment, this can beachieved via a pull wire, catheter or other pulling means coupled to thetether directly or indirectly.

In various embodiments, the tether can be a filament, cord, ribbon, etc.which would simply extend around the fronds to capture them like alasso. In one embodiment the tether can comprise a suture or suture-likematerial that is wrapped around the fronds. One or both ends of thesuture tether can be attachable to the balloon catheter 241. In anotherembodiment, tether 260 can comprise a band or sleeve that fits overfronds 220 and then expands with expansion of balloon 241. In this andrelated embodiments Tether 260 can also be attached to balloon catheter241. Also, tether 260 can be scored or perforated so that a portion ofthe tether shears or otherwise breaks upon balloon inflation, therebyreleasing the fronds. Further, the tether 260 can contain a radio-opaqueother medical image visible marker 260 m to allow the physician tovisualize the position of the tether on the fronds, and/or determine ifthe tether is constraining the fronds.

Referring now to FIGS. 8A-8B, in other embodiments of the deliverysystem 10, the fronds can be constrained through the use of a removablesleeve 270 that can be cover all or a portion of fronds 220 duringpositioning of the stent at the target tissue site and then be removedprior to deployment of the fronds. In one embodiment, sleeve 270 can beslidably advanced and retracted over stent 210 including fronds 220.Accordingly, all or portions of sleeve 270 can be made from lubricousmaterials such as PTFE or silicone. Sleeve 270 can also include one ormore radio-opaque or other imaging markers 275 which can be positionedto allow the physician to determine to what extent the sleeve iscovering the fronds. In various embodiments, sleeve 270 can be movablycoupled to catheter 240 such that the sleeve slides over either theouter or inner surface (e.g., via an inner lumen) of catheter 240. Thesleeve can be moved through the use of a pull wire, hypotube, stiffshaft or other retraction means 280 known in the medical device arts. Inone embodiment, sleeve 270 can comprise a guiding catheter or overtubeas is known in the medical device arts.

Referring now to FIGS. 9A-11B, an exemplary deployment protocol forusing delivery system 5 to deliver a stent having one or more frondswill be described. The order of acts in this protocol is exemplary andother orders and/or acts may be used. A delivery balloon catheter 30 isadvanced within the vasculature to carry stent 10 having fronds 16 to anos O located between a main vessel lumen MVL and a branch vessel lumenBVL in the vasculature, as shown in FIGS. 9A and 9B. Balloon catheter 30may be introduced over a single guidewire GW which passes from the mainvessel lumen MVL through the os O into the branch vessel BVL.Optionally, a second guidewire (not shown) which passes by the os O inthe main vessel lumen MVL may also be employed. Usually, the stent 10will include at least one radiopaque marker 20 on stent 10 located nearthe transition region between the scaffold section 12 and thecircumferential fronds 16. In these embodiments, the radiopaque marker20 can be aligned with the os O, typically under fluoroscopic imaging.

During advancement, the fronds are radially constrained by aconstraining means 250 c described herein (e.g., a cuff or tether) toprevent divarication of the fronds from the delivery catheter. When thetarget tissue location is reached at os O or other selected location,the constraining means 250 c is released by the expansion of balloon 32or other constraint release means described herein (alternatively, theconstraining means can be released prior to balloon expansion). Balloon32 is then further expanded to implant the scaffold region 10 within thebranch vessel lumen BVL, as shown in FIGS. 10A and 10B. Expansion of theballoon 32 also partially deploys the fronds 16, opening them in apetal-like manner, as shown in FIG. 10B, typically extending bothcircumferentially and axially into the main vessel lumen MVL. The fronds16, however, are not necessarily fully deployed and may remain at leastpartially within the central region of the main vessel lumen MVL.

Various approaches can be used in order to fully open the fronds 16. Inone embodiment, a second balloon catheter 130 can be introduced over aguidewire GW to position the balloon 132 within the petals, as shown inFIGS. 11A and 11B. Optionally, the first catheter 30 could bere-deployed, for example, by partially withdrawing the catheter,repositioning the guidewire GW, and then advancing the deflated balloon32 transversely through the fronds 16 and then re-inflating balloon 32to fully open fronds 16. As it is generally difficult to completelydeflate the balloon, however, and a partially inflated balloon would bedifficult to pass through the fronds, it will generally be preferable touse a second balloon catheter 130 for fully deforming fronds 16. Whenusing the second balloon catheter 130, a second GW will usually bepropositioned in the main vessel lumen MVL past the os O, as shown inFIGS. 11A and 11B. Further details of various protocols for deploying astent having fronds or anchors, such as stent 10, are described inco-pending application Ser. No. 10/807,643.

In various embodiments for methods of the invention using deliverysystem 5, the physician can also make use of additional stent markers 22and 24 positioned at the ends of stent 10. In one embodiment, one ormore markers 22 are positioned at the ends of the fronds as is shown inFIGS. 9A and 9B. In this and related embodiments, the physician canutilize the markers to ascertain the position of the stent as well asthe degree of deployment of the fronds (e.g., whether they are incaptured, un-captured or deployed state). For example, in one embodimentof the deployment protocol, the physician could ascertain properpositioning of the stent by not only aligning the transition marker 20with the Os opening O, but also look at the relative position of endmarkers 22 in main vessel lumen MVL to establish that the fronds arepositioned far enough into the main vessel, have not been inadvertentlypositioned into another branch vessel/lumen and are not hung up onplaque or other vessel blockage. In this way, markers 20 and 22 providethe physician with a more accurate indication of proper stentpositioning in a target location in a bifurcated vessel or lumen.

In another embodiment of a deployment protocol utilizing markers 22, thephysician could determine the constraint state of the fronds (e.g.capture or un-captured), by looking at the position of the markersrelative to balloon 30 and/or the distance between opposing fronds. Inthis way markers 22 can be used to allow the physician if the frondswere properly released from the constraining means prior to theirdeployment. In a related embodiment the physician could determine thedegree of deployment of the fronds by looking at (e.g., eyeballing) thedistance between markers 22 on opposing fronds using one or medicalimaging methods known in the art (e.g., X-ray angiography). If one ormore fronds are not deployed to their proper extent, the physician coulddeploy them further by repositioning (if necessary) and re-expandingballoon catheters 30 or 130.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Also, elements or steps from one embodiment can be readilyrecombined with one or more elements or steps from other embodiments.Therefore, the above description should not be taken as limiting thescope of the invention which is defined by the appended claims.

1. A method for delivering a luminal prosthesis, said method comprising:providing a delivery catheter which carries the prosthesis, wherein theprosthesis comprises a radially expansible scaffold section and at leasttwo anchors extending axially from an end thereof; advancing thedelivery catheter to position the prosthesis at a target location in abody lumen, wherein at least the anchors are radially constrained toprevent divarication from the delivery catheter; releasing the radialconstraint; and expanding the scaffold within the lumen.
 2. A method asin claim 1, wherein releasing and expanding occur simultaneously orreleasing occurs during expanding.
 3. A method as in claim 2, whereinthe radial constraint comprises folds of a balloon covering the anchors,wherein the constraint is released as the balloon is inflated.
 4. Amethod as in claim 2, wherein the radial constraint comprises a cuffwhich extends over the anchors.
 5. A method as in claim 2, wherein theconstraint comprises a tether which ties the anchors together, whereinthe tether is broken by expansion of the scaffold.
 6. A method as inclaim 1, wherein the radial constraint is released prior to expandingthe scaffold.
 7. A method as in claim 6, wherein the radial constraintcomprises a cuff which extends over the anchors, wherein the cuff iswithdrawn from the anchors prior to expansion of the scaffold.
 8. Amethod as in claim 7, wherein prior to withdrawal, the cuff extends overat least a portion of the scaffold.
 9. A method as in claim 6, whereinthe radial constraint comprises a tether which ties the anchorstogether, wherein the tether is withdrawn prior to expansion.
 10. Amethod as in claim 1, wherein expanding the scaffold deforms the anchorsto circumscribe at least a portion of the main-body lumen.
 11. A methodas in claim 1, wherein the prosthesis is deployed across an os openingfrom a main body lumen to a branch body lumen, the method furthercomprising: positioning the prosthesis so that the scaffold lies withinthe branch body and the at least two anchors extend into the main bodylumen; and circumferentially deforming the anchors to circumscribe atleast a portion of the main vessel wall and open a passage through theanchors.
 12. A method as in claim 10, wherein at least threecircumferential anchors extend into the main body lumen.
 13. A method asin claim 10, wherein positioning the prosthesis comprises aligning avisible marker on at least one of the prosthesis and a delivery balloonwith the os.
 14. A method as in claim 10, wherein the lumens are bloodvessels.
 15. A method as in claim 10, wherein the scaffold is expandedwith a balloon expanded within the scaffold.
 16. A method as in claim15, wherein the anchors are deformed by expanding a balloon positionedtransversely through the anchors.
 17. A method as in claim 16, whereinthe scaffold and anchors are expanded and deformed by the same balloon.18. A method as in claim 16, wherein the scaffold and anchors areexpanded and deformed by different balloons.
 19. A method as in claim11, further comprising deploying a second prosthesis within the passagethrough the anchors.
 20. A method as in claim 19, wherein the secondprosthesis is deployed by a balloon catheter exchanged over a guidewirepre-positioned for deformation of the anchors.
 21. A method as in claim19, wherein the anchors are deformed by deployment of the secondprosthesis.
 22. A method as in claim 19, wherein the deployed secondstent supports the anchors over their lengths from the os over the mainbody lumen wall.
 23. A prosthesis delivery system comprising: a deliverycatheter having an expandable member; a prosthesis carried over theexpandable member, said prosthesis having a radially expandable scaffoldsection and at least two anchors extending axially from an end thereof;and means for capturing at least the anchors to prevent the anchors fromdivaricating from the expandable member as the catheter is advancedthrough a patient's vasculature.
 24. A prosthesis delivery system as inclaim 23, wherein the capturing means comprises a portion of theexpandable member which is folded over the anchors.
 25. A prosthesisdelivery system as in claim 24, wherein the folds are formed throughaxial gaps between adjacent anchors.
 26. A prosthesis delivery system asin claim 23, wherein the capturing means comprises a cuff.
 27. Aprosthesis delivery system as in claim 26, wherein the cuff isconfigured to release the anchors as the expandable member is expanded.28. A prosthesis delivery system as in claim 26, wherein the cuff isconfigured to be withdrawn prior to deployment of the expandable member.29. A prosthesis delivery system as in claim 26, wherein the cuff isconfigured to shorten axially as it is expanded by the expandablemember.
 30. A prosthesis delivery system as in claim 26, wherein atleast a portion of an interior surface of the cuff comprises afluoropolymer.
 31. A prosthesis delivery system as in claim 26, whereina distal portion of the cuff has a different durometer than a proximalportion.
 32. A prosthesis delivery system as in claim 26, wherein thecuff is folded over the anchors.
 33. A prosthesis delivery system as inclaim 28, wherein the cuff extends over at least a portion of thescaffold prior to being released.
 34. A prosthesis delivery system as inclaim 23, wherein the capturing means comprises a tether whichcircumscribes the proximal portion of the prosthesis.
 35. A prosthesisdelivery system as in claim 34, wherein the tether is configured to bedetached from the anchors prior to expansion of the expandable member.36. A prosthesis delivery system as in claim 35, wherein the tether isconfigured to break upon expansion of the expandable member.
 37. Aprosthesis delivery system as in claim 23, wherein the prosthesiscomprises at least three circumferential anchors extending axially fromthe end of the scaffold.
 38. A prosthesis delivery system as in claim23, wherein the anchors have an axial length which is at least 1.5 timesthe width of the scaffold prior to radial expansion.
 39. A prosthesisdelivery system as in claim 23, wherein the anchors have an axial lengthof at least 2 mm.
 40. A prosthesis delivery system as in claim 23,wherein the scaffold comprises a plurality of axially adjacent cells.41. A prosthesis delivery system as in claim 23, wherein thecircumferential anchors are all congruent.
 42. A prosthesis deliverysystem as in claim 23, wherein the circumferential anchors will radiallyexpand when the scaffold is radially expanded.
 43. A prosthesis deliverysystem as in claim 23, wherein the circumferential anchors are adaptedto both bend and rotate relative to a control axis of the prosthesis.44. A prosthesis delivery system as in claim 23, further comprising aradiopaque marker at or near a transition location between the scaffoldand the circumferential anchors.
 45. A prosthesis delivery system as inclaim 23, wherein the system is configured to be mounted on a balloonhaving a radiopaque marker aligned with a transition location betweenthe scaffold and the circumferential anchors.